Pouch batteries are known that have a cell stack encapsulated in a laminate film exterior body.
In a pouch battery, creases generated at portions of the laminate film exterior body that cover the main sides of the cell stack result in uneven constraining pressure being applied to the cell stack when the pouch battery is constrained, producing an adverse effect on the battery performance and especially on the long-term cycle characteristic. Therefore, techniques for minimizing formation of creases in laminated exterior bodies have been proposed.
For example, PTL 1 describes a method for producing a pouch battery comprising:
a forming step in which a laminate film is formed into a cup section that can receive a flat-shaped cell stack,
a housing step in which the flat-shaped cell stack is housed into the formed laminate that has been formed in the forming step, and
a sealing step in which the opening of the cup section of the formed laminate is covered with a laminated sheet and sealed in a state of reduced pressure,
wherein the length of the bottom of the cup section formed in the forming step, in the direction along at least one side, is longer than the length of the cell stack housed in the housing step.
In the pouch battery produced by the method of PTL 1, the bottom of the cup section formed in the laminate film exterior body has a shape protruding outward from the lateral sides of the cell stack, along the main sides of the cell stack, and folded over from the protruding end and connected to the side of the cup section.